This invention concerns a contact lens for observation or irradiation of the eye.
Contact lenses of various types are used in opthalmology for observation or treatment of the eye by irradiation, notably, for treatment of the anterior chamber of the eye.
The contact lenses most often used to date have been the Koeppe contact lens and the Goldman type contact lens. The use of such lenses was described, in particular, in the published work entitled "Gonioskopie und Goniofotographie" by Winfried Muller and Hans-Peter Brandt, Ferdinand Enke Verlag Stuttgart 1979.
The Koeppe contact lens is a lens having a convex beam entry face and an approximately spherical exit face designed to be applied to the transparent zone of the cornea. Those lenses, however, have so far been used only for observation of the eye. The size of those lenses was primarily designed to obtain an image of the anterior chamber of the eye with a magnification factor of 20 to 30 in the course of the observation procedures.
The Goldmann type contact lens contains essentially one flat radiation entry face, one approximately spherical exit face designed to be applied to the transparent zone of the cornea and at least one reflecting face or wall making possible indirect observation of the anterior chamber of the eye by total reflection of the beams on that wall.
In spite of their undeniable intrinsic qualities for observation procedures, such as manageability, ease and convenience of use for the ophthalmologist, as far as the Goldmann type contact lens is concerned, those two types of lenses do not allow for treatment of the eye by irradiation with guaranteed safety for the patient, reliability and reproducibility of treatment, especially with high-energy irradiation by laser beam. In fact, in that type of treatment, one essential objective is to obtain a sufficient energy density to produce, by optical breakdown of the dielectric medium inside the eye, a pressure wave capable of assuring perforation of adjoining walls of the anterior chamber of the eye. However, patient safety factors in the course of those treatments demand a maximum reduction of the radiated energy density at the cornea-contact lens junction in order to prevent injury by the latter in the zone of entry of the laser beam into the eye. Furthermore, in order to assure, on each laser pulse firing, conditions of reproducibility and stability of emission of the pressure wave (shock wave) in the eye, it is indispensable for the contact lens, by its qualities of shape and composition, to afford the best possible focusing of the useful laser beam and the maintenance of its focussing qualities for any point of the eye and, mainly, of the anterior chamber of the eye.
The contact lenses of the prior art do not provide all of the conditions necessary for a reliable, safe and consistent treatment. In particular, it has been verified that the use of Goldmann type contact lenses, as previously described, does not make it possible, under some conditions of use, i.e., definitely, for certain points of the anterior chamber, to obtain sufficient energy at the focusing point to produce, by optical breakdown, emission of the desired pressure wave. In fact, the optical breakdown phenomenon for these points is likely to be obtained only at the cost of a substantial increase of radiated energy density of the beam, that increase, by a factor of at least 2 to 3, being prohibitive, due to the risks of injury to the cornea and damage to the contact lens itself.
This invention makes it possible to remedy those problems and involves the use of a contact lens for observation and treatment of the anterior chamber of the eye.
Another object of this invention is to provide a contact lens which enables by laser irradiation of the eye through that lens, to obtain the optical breakdown and pressure wave phenomenon of the medium inside the eye with energy radiated by the beam that is as low as possible.
Another object of this invention is to provide a contact lens enabling an optical breakdown phenomenon that is stable and well localized spatially, that same contact lens enabling appreciably identical effects to be obtained, from the clinical standpoint, for identical parameters of laser emission.
A further object of this invention is to provide a contact lens, for which all of the above-mentioned characteristics must remain appreciably constant, regardless of the firing point in the eye or, for a fixed firing point, regardless of the relative positions of the laser beam and of the contact lens in relation to the eye.
The contact lens according to the invention comprises for useful radiation, an entry face, a surface reflecting by total reflection and an approximately spherical exit surface, characterized in that the entry surface constitutes, for useful radiation, a wave surface.
Such contact lenses can be used in eye surgery, notably, for the diagnosis and treatment of conditions such as glaucoma or cataracts. For further details on this subject, one can refer to European patent application No. 80 810 357.6 and American patent application No. 211,207 now U.S. Pat. No. 4,409,979 and Ser. No. 211,202 now U.S. Pat. No. 4,391,275 in the applicant's name.